1. Field of the Invention
The present invention relates to a solar cell module which includes a photovoltaic element, a light receiving surface side protective member disposed above a light receiving surface of the photovoltaic element, and a back surface side protective member disposed above a back surface opposite to the light receiving surface of the photovoltaic element.
2. Description of the Related Art
Heretofore, a photovoltaic element, which includes a transparent conductive film formed of indium oxide layers, is known. For such an indium oxide layer, ITO (Indium Tin Oxide) being In203 to which SnO2 is added as impurities has been widely used because of its high conductivity and of good workability.
When using the above-described ITO as a transparent conductive film, it is known that the arithmetic mean roughness (Ra) of an ITO surface is made small so that it is 2.0 nm or less, to maintain low resistance and low light absorption (refer to, for example, Japanese Patent Application Laid-open Publication No. 2005-175160).
Further, a technology is disclosed in which, by using an indium oxide layer to which tungsten (W) is added as impurities, resistance and light absorption lower than those of the ITO can be maintained (refer to, for example, Japanese Patent Application Laid-open Publication No. H7-278791).
As described above, on the indium oxide layer, many trials have been conducted to achieve low resistance and high light transmittance.
On the other hand, when mounting a photovoltaic element on a solar cell module, there is high possibility that it is open to the outside air for a long period. However, no study has been made on weather resistance such as moisture resistance under the above condition. Particularly, when using a film as the back surface side protective member disposed above a back surface of a photovoltaic element, the entering of moisture due to deterioration of the film is considered. Accordingly, it is desired that a photovoltaic element having excellent moisture resistance be developed.